The present disclosure relates generally to bone joint prostheses. More specifically, it concerns embodiments of prostheses for joints or other injured parts of the body which may deliver increased joint stability yet allow for normal flexion and extension motion. Exemplary joints may include the knee, hip, wrist, and elbow, although other prostheses are additionally contemplated within the scope of the invention.
Orthopedic prostheses are commonly utilized to replace damaged bone and tissue in the human body. Artificial joint replacement is a widely accepted successful medical procedure for the treatment of arthritic or deformed joints. Hundreds of thousands of joint replacement procedures are performed every year. Prosthetic hip and knee replacement comprise the vast majority of these procedures; however, many other joints may be treated as well including, but not limited to, the shoulder, elbow, wrist, ankle, and temporomandibular joints. For example, a prosthetic knee implant may be used to restore natural knee function by repairing damaged or diseased articular surfaces of a femur, a tibia, or both. Additionally, there are other joints and residual limbs, such as the intervertebral disk joint of the spine, which are not commonly replaced with prosthetic joints, but which might be amenable to such treatment to remedy disease states if sufficiently durable materials in functional designs were available.
The ideal total artificial joint prosthesis may be characterized in terms of its durability. The mechanical parts of the joint (otherwise known as an articulation) should function without wearing out or breaking. Further, the implant's fixation to the recipient's skeleton should remain rigidly intact for the duration of the recipient's lifetime without requiring restrictions on the intensity of activities or the degree of load bearing beyond those which would apply to a natural joint. Currently available devices fall short of fulfilling these criteria in one or more significant ways.
For example, polyethylene bearings may wear out after between 5 and 20 years of service, depending upon factors such as a patient's age, weight, and activity level. The younger and more active the patient, the shorter the anticipated functional life of the implant. Thus, those patients who, because of their youth, need the greatest durability from their implants, typically receive the exact opposite.
Further, the generation of particulate debris (or wear particles) which results from normal wear often causes inflammatory reactions in the bone surrounding and anchoring the implants, which can result in severe erosion of the bone. The immune system's inflammatory reaction to particulate debris—or “osteolysis”—has proven to be a most prevalent cause of failure of ratification joints requiring subsequent artificial joint replacement. This is because osteolysis may cause loosening of the critical implant-bone fixation, and may result in increased risk of fracture of the bone around the implants. It is also the cumulative effect of continual wear of the polyethylene that results in wear-through of the mechanical joint and ultimate bearing failure.
In order to reduce the risks of dislocation, recipients of artificial joints may be required to restrict their range of motion in normal activities, compromising their ability to engage in many routine activities which would otherwise be possible with normal natural joints. In order to decrease the rate of bearing wear which leads to implant failure and/or problems resulting from debris related osteolysis, patients may also be required to restrict their activities in terms of intensity and duration relative to that routinely possible with normal natural joints.
Unsurprisingly, wear-through of the components and/or periprosthetic osteolysis of the host bone with associated implant loosening and/or periprosthetic bone fracture requires major surgical intervention to remove the failed implants, reconstruct the damaged bone, and replace the failed prosthesis with a new artificial joint. This revision surgery is typically much more complicated than the initial implant surgery, and carries with it increased risks for perioperative complications, as well as increased risks for implant failure as compared to primary artificial joint replacement. Subsequent failures require further complex surgical intervention, with continually increasing risks of perioperative complications and early implant failure with each episode.
Additionally, prosthetics face similar wear-down issues as artificial joints. The ideal prosthetic limb may be characterized in terms of its durability and impact absorption. For example, among the features desirable in a prosthesis is the incorporation of some means for providing impact absorption and/or damping during use of the prosthesis without sacrificing the ability to reliably and predictably support the amputee's body weight. Such impact absorption permits the amputee to participate in activities with comfort and minimal residual limb trauma, hence allowing the amputee to be mobile for longer periods of time. Also desirable is a convenient means to selectively adjust the degree of impact absorption to suit the particular attributes (e.g., weight) and activity (e.g., walking, running, jumping, etc.) of the amputee.
It is an object of the current disclosure to improve upon prior prosthetic technologies for increasing life of an implant and/or a prosthetic by reducing the wear and decreasing the shedding of significant amounts of particles as a result of normal use of the prosthetic and increasing the damping effects of the implant and/or prosthetic.